Danielle a hurricane; TD 7 forming off coast of Africa

Hurricane Danielle has stopped intensifying and is now looking a bit ragged this morning, but remains a respectable Category 1 hurricane with 80 mph winds. The intensity of Danielle's heavy thunderstorms has waned in the past few hours, and the organization of the storm is less impressive. This is probably due do strong upper-level winds out of the west that are creating a moderate 10 - 20 knots of wind shear, and injecting some of the dry air from the Saharan Air Layer (SAL) that surrounds Danielle. Danielle is over warm 28°C water, but is far from any land areas.

Figure 1. Morning satellite image of Tropical Storm Danielle (left side of image) and the forming Tropical Depression Seven (right side of image.)

Forecast for DanielleA powerful trough of low pressure over the mid-Atlantic Ocean will begin to pull Danielle more to the northwest by Wednesday, keeping Danielle well to the east of Bermuda. Most of the models predict that this trough will be strong enough to fully recurve Danielle out to sea. It is possible that Danielle could eventually threaten Newfoundland, Canada, but it currently does not appear that any other land areas will be at risk from this storm. History suggests that a storm in Danielle's current location has only a 20% chance of making landfall on the U.S. East Coast. If Danielle passes east of Bermuda, as forecast, these percentages drop to less than 5%. As far as intensity goes, it is looking unlikely that Danielle will attain major hurricane status (115+ mph winds.) There is enough dry air and wind shear affecting the storm today that it will take several days for the storm to recover its strength, making it less likely the storm can hit Category 3.

The formation of Danielle is remarkable in this it was successfully forecast by the GFS model nearly two weeks in advance. The ECMWF and NOGAPS models also did a good job of predicting Danielle's formation a week in advance. The models are getting better and better each year at forecasting genesis of tropical cyclones, though a successful 1-week forecast of genesis is still a rarity. For example, none of the models foresaw the development of 96L until just 3 - 4 days ago.

Figure 2. Plot showing historically the percent chance of a tropical cyclone in a given location impacting the U.S. East Coast. For storms in Danielle's current position (orange hurricane symbol), about 20% of them go on to hit the U.S. East Coast. For storms in 96L's current location (red circle with a "?" in it), the odds are also 20%. Image credit: Bob Hart, Florida State University.

96L (soon to be Tropical Depression Seven)Satellite images suggests that a tropical wave (96L) that emerged off the coast of Africa yesterday morning has developed a closed circulation, low-level spiral bands, and an increasing amount of heavy thunderstorms. While this morning's ASCAT pass does not show a clear closed circulation, satellite estimates of 96L's strength support calling this a 30 mph tropical depression. It is likely that this storm will be designated Tropical Depression Seven later today. 96L is already bringing heavy rain and strong, gusty winds to the southern Cape Verde Islands. Winds were sustained at 26 mph at Mindelo in the northwest Cape Verde Islands this morning, and 24 mph at Praia, the station closest to the center of 96L. Both stations were reporting widespread dust, due to strong winds blowing Saharan dust from the coast of Africa. However, water vapor satellite images show that only a modest amount of dry air is accompanying this dust, and dry air is currently not a major detriment to 96L. Wind shear is about 10 - 20 knots, and sea surface temperatures are warm, 28°C.

Forecast for 96L/Tropical Depression SevenWind shear is predicted to remain low, 5 - 10 knots, for the next four days. SSTs will cool a bit to 27°C by Thursday, but this is still above the 26.5°C threshold for hurricane development. Dry air will probably be the main inhibiting factor for 96L. Most of the intensity forecast models bring 96L to hurricane strength by four days from now, and this is a reasonable forecast. 96L should become Tropical Storm Earl later today or on Wednesday, and will probably bring sustained winds of 40 mph to the southernmost Cape Verdes Islands tonight and Wednesday.

The long range fate of 96L remains unclear. The storm is being steering by the same ridge of high pressure steering Danielle, and will initially follow a track similar to Danielle. 96L may encounter the cold waters stirred up by Danielle at times this week, inhibiting development. As 96L approaches the central Atlantic five days from now, the storm will encounter the same mid-Atlantic trough that will be steering Danielle, and 96L should turn more to the northwest. It is unclear at this point whether this trough will be strong enough to fully recurve 96L out to sea, east of Bermuda. This will, in part, depend upon how strong Danielle gets. A stronger Danielle is likely to create more of a break in the ridge of high pressure steering 96L, encouraging the storm to turn north and recurve out to sea. A weaker Danielle will make 96L more likely to miss recurvature, and follow a track to the west or west-northwest towards the U.S. East Coast early next week. History suggests that a storm in 96L's current location has only a 20% chance of making landfall on the U.S. East Coast.

When will the Caribbean and Gulf of Mexico get active?The large scale atmospheric circulation over the Caribbean and Gulf of Mexico currently features relatively dry, stable, sinking air. This is due, in part, to the Madden-Julian oscillation (MJO). The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased. The latest MJO forecast from the GFS model calls for the wet phase of the MJO to move into the Caribbean during the first week of September. However, keep in mind that forecasts of MJO activity 1 - 2 weeks in advance are not very skillful. The GFS model forecast of MJO activity made two weeks ago did fairly well for the first week, but poorly for the second week of the forecast.

Tropical Storm Frank spares MexicoOver in the Eastern Pacific, Tropical Storm Frank has moved away the coast far enough from the Mexican coast to no longer pose a heavy rainfall threat, and all tropical storm warnings have been dropped.

"Hurricane Haven" airing again this afternoonTune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. I'll focus on Danielle, Earl, and Frank, and discuss the possibilities of a hyperactive Atlantic hurricane period coming during the first week of September.

Anyway, these were some of the main guys making some pretty unscientific comments..LOL...if I could describe it it would be a bunch of guys in a room who jumped up and down and began to hug one another as the GFS results were announced!!!! Whew!!!

Was like a great touchdown pass to win the game.....lots of hype.....and of course.....going to blow NEW YORK away...lol

Anywat, these were some of the main guys making some unscientific comments..LOL...if I coul describe it it would be a bunch of guys in a room who jumped up and down and began to hug one another as the GFS results were announced!!!! Whew!!!

Anyway, these were some of the main guys making some pretty unscientific comments..LOL...if I could describe it it would be a bunch of guys in a room who jumped up and down and began to hug one another as the GFS results were announced!!!! Whew!!!

Anyway, these were some of the main guys making some pretty unscientific comments..LOL...if I could describe it it would be a bunch of guys in a room who jumped up and down and began to hug one another as the GFS results were announced!!!! Whew!!!

SUBJECT: "FRANK" Strengthens A Little And Moves Further Away From The Southwestern Coast Of Mexico

At 9:00 AM UTC, Tropical Storm Frank (991 hPa) located at 16.2N 103.6W or 175 NM south southeast of Manzanillo, Mexico has sustained winds of 60 knots with gusts of 75 knots. The cyclone is reported as moving west northwest at 8 knots.

.SYNOPSIS...TROUGH FROM NEAR FLORIDA PANHANDLE TO S TEXAS WILL DRIFT W AND EXTEND FROM MOBILE BAY TO 24N94W WED NIGHT THEN MOVE ACROSS THE WESTERN GULF THROUGH THU NIGHT AND APPROACH THE TEXAS COAST FRI AND MOVE INLAND LATE FRI INTO SAT. HIGH PRES WILL BUILD SW ACROSS AREA BEHIND THE TROUGH LATE FRI THROUGH SUN.

Quoting Cotillion:NEAR THE END OF THE FORECAST PERIOD...DYNAMICALGUIDANCE SHOWS A SIGNIFICANT INCREASE IN SHEAR SO THE HURRICANEWILL PROBABLY BE ON A WEAKENING TREND BY DAY 5. THE OFFICIALINTENSITY FORECAST IS CLOSE TO THE NUMERICAL INTENSITY CONSENSUS.

NEAR THE END OF THE FORECAST PERIOD...DYNAMICALGUIDANCE SHOWS A SIGNIFICANT INCREASE IN SHEAR SO THE HURRICANEWILL PROBABLY BE ON A WEAKENING TREND BY DAY 5. THE OFFICIALINTENSITY FORECAST IS CLOSE TO THE NUMERICAL INTENSITY CONSENSUS.

ALTHOUGH THE CLOUD PATTERN OF THE HURRICANE HAS NOT BECOME MUCHBETTER ORGANIZED ON GEOSTATIONARY IMAGERY...AN AMSR-E PASS FROM0516 UTC SUGGESTS AN EYE WITH FAIRLY WELL-DEFINED INNER CORECONVECTIVE BANDING ON THE 37-GHZ CHANNEL. CIRRUS-LEVEL OUTFLOW ISBECOMING A LITTLE BETTER DEFINED TO THE NORTHWEST. USING A BLENDOF DVORAK CURRENT INTENSITY ESTIMATES FROM TAFB AND SAB...THEADVISORY INTENSITY IS SET TO 70 KT. AN UPPER-LEVEL CYCLONE TO THENORTH-NORTHWEST OF THE HURRICANE HAS BEEN IMPARTING MODERATEWEST-SOUTHWESTERLY SHEAR ON DANIELLE. GLOBAL MODEL GUIDANCEINDICATES THAT THIS UPPER-LEVEL CYCLONE SHOULD MOVE SOUTHWEST OVERTHE NEXT 24 TO 48 HOURS. THIS EVOLUTION WOULD CAUSE THE SHEAR TOWEAKEN AND BECOME MORE SOUTHERLY OR EVEN SOUTHEASTERLY. BOTH OFTHESE ENVIRONMENTAL FACTORS SHOULD BE MORE CONDUCIVE FORSTRENGTHENING. NEAR THE END OF THE FORECAST PERIOD...DYNAMICALGUIDANCE SHOWS A SIGNIFICANT INCREASE IN SHEAR SO THE HURRICANEWILL PROBABLY BE ON A WEAKENING TREND BY DAY 5. THE OFFICIALINTENSITY FORECAST IS CLOSE TO THE NUMERICAL INTENSITY CONSENSUS.

THERE HAS BEEN A GRADUAL DECREASE IN FORWARD SPEED AND THE INITIALMOTION IS NOW ESTIMATED TO BE ABOUT 300/15. A TURN TOWARD THENORTHWEST IS LIKELY TO OCCUR VERY SOON IN RESPONSE TO A WEAKNESS INTHE SUBTROPICAL RIDGE TO THE NORTH OF DANIEL. A SHORT WAVEMID-TROPOSPHERIC RIDGE WILL BE PASSING TO THE NORTH OF THEHURRICANE IN A COUPLE OF DAYS. THIS WOULD TEMPORARILY HALT AFURTHER TURN TO THE RIGHT...UNTIL THE RIDGE MOVES FARTHER EAST. LATER ON...A MORE NORTHWARD MOTION IS LIKELY AS DANIELLE MOVESAROUND THE WESTERN PERIPHERY OF THE RIDGE AND IS INFLUENCED BY ATROUGH MOVING OFF THE NORTHEAST U.S. COAST. THE OFFICIAL TRACKFORECAST IS QUITE CLOSE TO THE DYNAMICAL MODEL CONSENSUS. ITSHOULD BE NOTED THAT THE LATEST ECMWF FORECAST IS AN OUTLIER...SHOWING A SHARPER TURN TO THE RIGHT THAN MOST OF THE MODELS...ANDIS SIGNIFICANTLY FASTER THAN THE OTHER TRACK GUIDANCE. IT WILL BEINTERESTING TO SEE IF THAT MODEL TURNS OUT TO BE CORRECT.

IF.....it follows the center line of the track it would pass at least 150 miles east of Bermuda. IF it does they will come out okay with Danielle. The 34 knot winds extend 90 miles to her NW right now.

Quoting flibinite:Just a question here, for all you late-nighters... if you could do some weather modification that basically disrupts eyewall formation, and given you couldn't do it too close to land, where it would be spotted on land-based radars, how would you do it?

Would you bang away at DMAX, thus keeping the cyclone from gaining too much strength, keeping in mind you want it to have some strength so that it tries its best to move poleward and go out to sea (if it's a CV cyclone)?

I know that's how I'd do it, leaving the NHC and Dr. Masters to wonder how a perfectly good eyewall, ala Monday, just collapsed as it did, and why once again Danielle seems to be failing overnight, when one could assume it should be getting stronger, perhaps.

There isn't a tropical cyclone that hasn't followed this pattern this year, btw, and the only good excuse is that they've been "monsoonal", and thus too big to ever "wrap their arms in".

Not saying that's the case for sure, mind you, but nothing in the past few years has proved this theory wrong, when one takes into account our not caring about Mexico, Bermuda, or Newfoundland so very much, really.

its more about the fact that it slowed down in fwd speed enough for the ull and more so the dry air to make it start to wane; last night idk, even the nhc had no good answer and admitted such

Just a question here, for all you late-nighters... if you could do some weather modification that basically disrupts eyewall formation, and given you couldn't do it too close to land, where it would be spotted on land-based radars, how would you do it?

Would you bang away at DMAX, thus keeping the cyclone from gaining too much strength, keeping in mind you want it to have some strength so that it tries its best to move poleward and go out to sea (if it's a CV cyclone)?

I know that's how I'd do it, leaving the NHC and Dr. Masters to wonder how a perfectly good eyewall, ala Monday, just collapsed as it did, and why once again Danielle seems to be failing overnight, when one could assume it should be getting stronger, perhaps.

There isn't a tropical cyclone that hasn't followed this pattern this year, btw, and the only good excuse is that they've been "monsoonal", and thus too big to ever "wrap their arms in".

Not saying that's the case for sure, mind you, but nothing in the past few years has proved this theory wrong, when one takes into account our not caring about Mexico, Bermuda, or Newfoundland so very much, really.

I am glad to see Danielle get near the W Atlantic to really tell the tale of conditions out there. Right now it is showing it's not a bed of roses out there just like i thought. That upper level trough carved out in the W Atlantic has been there for over 2 months rotating ULL's with dry air. It wouldn't matter if Danielle came close to the EC IF those conditions stay in place. It would weaken quite a bit before making landfall.

True...that gap could close up faster than the models are showing. Right now Danielle looks like she is getting smacked once again and i wouldn't be surprised if she gets downgraded today. I don't think she is going to get that strong imo

i think she will wax and wane, maybe turn as a 1 max out as a 2, but the models show a strong 3, and the effect on the ridge between a strong 3 and a weak 2 is very very different, especially if D is a small weak 2, and she isnt that big right now.

Quoting smuldy:per future earl, the models right now are all making Danielle a monster storm which would leave a huge gap for Earl to follow, if Danielle is not a major that gap in the ridge will seal up alot quicker, and that will have as much influence as forward speed and where Danielle recurves as to whether future Earl will see a weakness at all, why it is way too early to tell until we see those 3 key factors that Danielle will set to sow the fields for future Earl to follow, assuming 96L makes it to Earl, which it likely will.

True...that gap could close up faster than the models are showing. Right now Danielle looks like she is getting smacked once again and i wouldn't be surprised if she gets downgraded today. I don't think she is going to get that strong imo

Quoting robert88:GFS is showing a pattern change in the extended outlook that should keep waves moving more W. The HP off the EC is expected to get stronger and move more E and links up with the Bermuda HP. September should be a crazy month if that verifies.

per future earl, the models right now are all making Danielle a monster storm which would leave a huge gap for Earl to follow, if Danielle is not a major that gap in the ridge will seal up alot quicker, and that will have as much influence as forward speed and where Danielle recurves as to whether future Earl will see a weakness at all, why it is way too early to tell until we see those 3 key factors that Danielle will set to sow the fields for future Earl to follow, assuming 96L makes it to Earl, which it likely will.